Producing increased yield of hydrogen by cracking petroleum with potassium-containing catalyst

ABSTRACT

A petroleum cracking catalyst having thereon metals usually found in petroleum, e.g., iron, nickel and vanadium, is modified by addition of potassium to increase significantly the rate of hydrogen production when employing the thus-modified catalyst for cracking of petroleum.

This invention relates to the catalytic cracking of petroleum. In one ofits aspects the invention relates to the production of hydrogen bycracking petroleum in the presence of a catalyst. In a further aspect ofthe invention it relates to the preparation of a modified petroleumcracking catalyst suited to increasing production of hydrogen. In stillanother of its aspects the invention relates to the production ofpetroleum-cracking products, e.g., gasoline and hydrogen.

In one of its concepts the invention provides a process for themodification of a cracking catalyst which contains metals usually foundin petroleum, e.g., iron, nickel and vanadium, as in a catalyst whichhas been used for the catalytic cracking of petroleum, by adding theretopotassium or an equivalent alkali metal compound. In another of itsconcepts the invention provides a process for the catalytic cracking ofa petroleum oil to produce cracking products including a gasoline andhydrogen, the hydrogen being obtained in yield which is substantiallygreater than that obtained ordinarily with the usual cracking catalyst,by modifying the catalyst by the addition of an alkali metal, e.g.,potassium, thereto.

In certain refinery operations, e.g., hydrotreating operations,considerable quantities of hydrogen are consumed. One way in which toproduce hydrogen is to do so employing a cracking catalyst as in theproduction of gasoline. It is desirable to obtain increased yields ofhydrogen when cracking to produce gasoline without significant loss ofgasoline yield and without significant increase in production of coke,which must be expensively removed from the catalyst during regeneration.Energy considerations are involved in any such process as is well known.For example, the cost of compressing air for regeneration of thecatalyst by burning coke therefrom is significant. Further, in existingplants, there is limited capacity for regeneration of catalyst.Accordingly, it is helpful to have a catalyst and process for productionof hydrogen in increased quantities without materially increasing cokeproduction.

An object of the invention is to produce hydrogen from petroleum.Another object of the invention is to modify a petroleum crackingcatalyst in a manner such that increased quantities of hydrogen can beobtained when employing the modified catalyst to crack a petroleum oilfor hydrocarbon. A further object of the invention is to produceincreased quantities of hydrogen from a catalytic cracking petroleumprocess without significantly losing gasoline yield or increasingsignificantly coke production.

Other aspects, concepts, objects and the several advantages of theinvention are apparent from a study of this disclosure and the claims.

According to the present invention there is added to a catalyst used inthe cracking of a petroleum oil or hydrocarbon an alkali metal, e.g.,potassium, the catalyst also containing metals commonly found inpetroleum, e.g., iron, nickel and vanadium. The catalyst, preparedaccording to the invention, is employed, also according to theinvention, to crack a petroleum oil or hydrocarbon.

Such cracking catalyst materials can be any of those cracking catalystsconventionally employed in the catalytic cracking of hydrocarbonsboiling above 400° F. (204° C.) for the production of gasoline, motorfuel, blending components and light distillates. These conventionalcracking catalysts generally contain silica or silica-alumina. Suchmaterials are frequently associated with zeolitic materials. Thesezeolitic materials can be naturally occurring, or they can be producedby conventional ion exchange methods such as to provide metallic ionswhich improve the activity of the catalyst. Zeolite-modifiedsilica-alumina catalysts are particularly applicable in this invention.When used to crack feedstock that contains the metals commonly found inpetroleum, i.e., iron, nickel and vanadium, these metals tend toaccumulate on the catalyst. For the purpose of this invention thecracking catalyst should contain a minimum of 0.02 wt. percent of metalthat has been deposited on it during use.

Generally, the deposited metal will be a mixture containing all threeelements listed, but it may be predominantly or even exclusively any oneof the three. The maximum concentration of contaminating metals will belimited by the concentration at which the catalyst becomesinsufficiently active for cracking. Metal content, referred to here,does not include metals that were incorporated into the catalyst duringits manufacture. The latter are relatively unimportant because they aremuch less accessible to the hydrocarbon during cracking than are themetals that have been deposited on the active surface of the catalyst.

In view of results obtained with potassium experimentally, it appearsthat lithium, sodium, rubidium and cesium, the other members of Group Iaof the Periodic Table, will also be effective to enhance hydrogenproduction with metal-contaminated cracking catalysts.

The quantity of potassium required to treat the catalyst is in the rangeof from about 0.01 to about 0.5 wt. percent, expressed as the element.This is equivalent to 0.0026 to 0.128 milli-equivalents per gram ofcatalyst. The preferred concentration of added potassium is from about0.01 to about 0.1 wt. percent, equivalent to 0.0026 to 0.026milli-equivalents per gram of catalyst. The same atomic concentration ofthe other alkali metals should be used when they are substituted forpotassium. As above noted, these concentrations are in addition to thealkali metals that were incorporated into the catalyst during itsmanufacture.

Potassium, or another alkali metal compound, can be added to themetal-contaminated catalyst in a variety of ways with equallysatisfactory results. These include:

(1) Addition at regeneration conditions. A dilute solution, e.g., inwater, of a potassium compound is sprayed into the regenerator of acatalytic cracker, to treat uniformly the contained catalyst. (2)Addition in oil feed. A oil-soluble compound, e.g., potassium oleate, isdissolved in the petroleum feedstock to the catalytic cracker.

(3) Solution impregnation. The catalyst can be wetted with asolution-aqueous of organic- of an appropriate potassium compound. Afterremoval of the solvent by drying, the catalyst is ready for use.

As indicated, either oil-soluble or water-soluble compounds of potassium(or other alkali metals) are suitable to treat the cracking catalyst.Preferred compounds include the carbonate, bicarbonate, or hydroxide,and salts of carboxylic acids such as the acetate, butyrate, oroctadecanoate. Less preferable are compounds containing halogens. Underreaction conditions they tend to release the halogen, causing corrosionin the catalytic cracker.

Addition of potassium to a metal-contaminated catalyst has been shown toenhance significantly its rate of hydrogen production. It is believedthat similar results would be obtained if the addition of potassium wasconcurrent with the accumulation of iron, nickel and vanadium, and alsoif the potassium were added to the surface prior to the exposure of thecatalyst to metal-contaminated petroleum.

The cracking catalysts treated as described can be used similarly to theuse of untreated catalyst. Treated catalysts have been shown towithstand successfully regeneration at 1300° F. (740° C.), which ishotter than usually obtained in the regeneration.

Although the addition of a small amount of potassium (or another alkalimetal) to metal-contaminated cracking catalyst is effective to increasethe production of hydrogen, the quantity of added alkali must becarefully monitored. When the acid sites on the cracking catalyst havebeen neutralized, very little activity remains. A sufficiency of suchsites should be preserved.

Hydrogen produced with catalyst made by this invention will of necessitybe quite impure. Residue gas obtained as effluent from a plant treatingthe product of a catalytic cracker operating on metals-contaminatedcracking catalyst has composition typified in Table I.

The acid gases (hydrogen sulfide and carbon dioxide) are readily removedby scrubbing, and the remainder can be used without further treatment.Alternatively the hydrogen-containing stream can be subjected tocryogenic treatment from which essentially pure hydrogen is produced.

                  TABLE I                                                         ______________________________________                                        Residue Gas Composition                                                       ______________________________________                                        CO + N.sub.2  6.2 mole %                                                      CO.sub.2      2.9                                                             H.sub.2 S     5.3                                                             H.sub.2       30.1                                                            CH.sub.4      24.7                                                            C.sub.2 s     25.0                                                            C.sub.3 's    4.0                                                             C.sub.4 's    1.8                                                             ______________________________________                                    

EXAMPLES

Identical tests were made on five catalysts to illustrate the invention.

CATALYST 1

This was equilibrium zeolite catalyst taken from a cracking unit thatprocessed residuum. It contained 80% F-1000 (manufactured by FiltrolCorp.). Its surface area was 74.3 m² gm⁻¹ and, by analysis, contained0.38 wt. percent Ni, 0.60 wt. percent V, and 0.90 wt. percent Fe.

CATALYST 4

To 40 gm of Catalyst 1 being fluidized in a quartz reactor with 0.6 CFHair while being heated at about 1300° F. (704° C.) there was added,during 220 minutes, a solution containing 0.0394 gm potassium hydroxidedissolved in 100 ml water. Weight of recovered catalyst was 34.9 gm.This represents an addition of 0.073 wt. percent K to the catalyst.

CATALYST 3

To 32.8 gm of Catalyst 1 being fluidized in a quartz reactor withnitrogen while being heated at 950° F. (510° C.) there was added 0.0218gm potassium as a solution of potassium oleate dissolved in gas oil.This represents an addition of 0.066 wt. percent K to the catalyst.

CATALYST 5

A 150 gm portion of Catalyst 1 was wetted with 150 cc of water; to theresulting paste was added 0.0901 gm potassium (as potassium hydroxide)dissolved in 80 additional cc of water. After thorough mixing it wascompletely dried on a hot plate at above 400° F. (200° C.). Thistreatment represented the addition of 0.086 wt. percent potassium to thecatalyst.

CATALYST 2

To 40.11 gm of Catalyst 1 there was added 58 cc of water. The resultantpaste was permitted to stand at ambient conditions for several days,then dried on a hot plate in a manner similar to Catalyst 5. Thiscatalyst received no additional potassium, but was treated with wateronly.

These catalysts were evaluated in a fluidized bed reactor system usingstandardized conditions of 1300° F. (704° C.) for regeneration and 950°F. (510° C.) for reaction with topped crude oil for 0.5 minutes.Inspection data for the topped crude are presented in Table II. Thecatalyst to oil ratio was varied as needed to obtain the requiredconversion. The gas and liquid products were analyzed by gas liquidchromatography and the reactor was weighed to determined coke. Most runshad better than 95 percent material balance. A few runs with lowermaterial balance were discarded. The data points were smoothed by aleast squares method. Results at 75 vol. % conversion are given in TableIII.

                  TABLE II                                                        ______________________________________                                         Topped Crude Inspection Data                                                 ______________________________________                                        API gravity @ 60° F.                                                                       20.9                                                      Distillation, ASTM D-1160                                                     2% overhead          670° F.                                                                         (354° C.)                                10                   815     435                                              20                   895     479                                              30                   944     507                                              40                  1001     538                                              50                  1066     574                                              Carbon residue, Ramsbottom                                                                        5.6 wt. percent                                           Carbon              85.8   wt. percent                                        Hydrogen            11.8   wt. percent                                        Nitrogen            0.27   wt. percent                                        Sulfur              1.2    wt. percent                                        Nickel              5.24   ppm                                                Vanadium            5.29   ppm                                                Iron                29     ppm                                                Pour point          70° F.                                             Viscosity, SUS @ 210° F.                                                                   142                                                       ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        Effect of Adding Potassium to                                                 Metal-Contaminated Cracking Catalyst                                                        Yields                                                                 Wt. %                   Coke,                                                 K       Catalyst:                                                                              Gasoline,                                                                            wt. %  SCF H.sub.2 /bbl                        Catalyst                                                                             Added   Oil      vol %  of Feed                                                                              oil converted                           ______________________________________                                        1      None    7.4      54.8   16.4   800                                     2      None    6.3      57.3   15.5   875                                     3      0.066   6.7      57.7   15.9   955                                     4      0.073   7.4      55.7   16.0   974                                     5      0.086   7.0      58.5   17.1   983                                     ______________________________________                                    

All tests in which the original catalyst was modified resulted inhydrogen yield that was significantly greater than from the originalcatalyst. However, the increase obtained with Catalysts 3, 4 and 5, towhich potassium had been added, was at least twice as great as fromCatalyst 2, and furthermore the change in the activity of Catalyst 2 wasshort-lived when compared to the change in Catalysts 3, 4 and 5. Thedifference in the yield of coke from the catalysts is considered to beinsignificant. The yield of gasoline was appreciably increased withcatalysts 2, 3 and 5 over that obtained with Catalyst 1.

Reasonable variation and modification are possible within the scope ofthe foregoing disclosure and the appended claims to the invention theessence of which is that a cracking catalyst containing metals commonlydeposited thereon from petroleum cracked thereby is modified by additionof an alkali metal, e.g., potassium, in an amount sufficient tosignificantly increase the hydrogen production with said catalyst.

I claim:
 1. A petroleum cracking catalyst suited for cracking apetroleum hydrocarbon or oil, said oil containing metals commonly foundin petroleum, said catalyst being suitable for high gasoline production,under catalytic cracking conditions suited to produce high gasolineyields, modified with an amount of potassium sufficient to causeappreciable increase in hydrogen produced when said catalyst is employedfor cracking of said hydrocarbon or oil but insufficient to cause anysubstantial loss in gasoline yield when cracking under said conditions,the potassium being added to the catalyst in the range of from about0.01 to about 0.5 weight percent, calculated as the element.
 2. Acatalyst according to claim 1 wherein the potassium is present in anamount in the range of from about 0.01 to about 0.1 weight percent.
 3. Apetroleum cracking catalyst which has been used for cracking afeedstock, said feedstock containing metals commonly found in petroleum,said catalyst being suitable for high gasoline production, undercatalytic conditions suited to produce high gasoline yields, saidcatalyst having been modified by addition of a minor amount of potassiumthereto in the approximate range of from about 0.01 to about 0.5 weightpercent, expressed as the metal, sufficient to increase yield ofhydrogen otherwise obtained in said catalyst.
 4. A catalyst according toclaim 3 wherein the potassium is present in an amount in the range offrom about 0.01 to about 0.1 weight percent.